Clear cell and style cache when controlled-scroll mode Grid stops scr…

…olling. @leoasis - bvaughn#649)

Removed lingering React.PropTypes reference in InfiniteLoader.

Added prop-types dependency to avoid deprecation warnings for React 1…

…5.5+.

Added public animation-friendly API methods to Grid/List/Table for an…

… alternative to props-based animating. (@imadha - bvaughn#641)

Fixed an invalid import in a vendored file

* 🎉 WindowScroller and Grid now support horizontal window-scrolling v…

…ia new autoWidth property. (@maxnowack - PR bvaughn#644)

* 🐛 Fixed a Content Security Policy (CSP) issue in an upstream dependency that impacted users of the Masonry component. For more information see issue bvaughn#640.
* ✨ List and Table always overscan 1 row in the direction _not_ being scrolled to better support keyboard nativigation (via TAB and SHIFT+TAB). For more information see issue bvaughn#625.
* ✨ Grid no longer alters scroll direction for one axis (eg vertical) if a scroll event occurs for another axis (eg horizontal).

Grid supports state-override of isScrolling value via new isScrolling…

… prop. This enables cache-while-scrolling of cells when used with WindowScroller. (@olavk - bvaughn#639)

🐛 Small accessibility fix to MultiGrid so that focus outline shows th…

…rough by default for main (bottom/right) Grid. Top and left Grids are also not tab-focusable by default now since they are scroll-observers anyway.

✨  Added columnWidth parameter to ColumnSizer and deprecated getColumnWidth callback. The callback was not necessary since columnWidth doesn't change without a re-render and fixed number values perform better in Grid due to some internal optimizations anyway.

* 🐛 Edge-case InfiniteLoader bug fix; prevent jumping to the first ro…

…w when scrolling fast. ([@reVrost](https://github.com/reVrost) - [bvaughn#632](bvaughn#632))

* 🐛  Reverted unexpected regression from [bvaughn#616](bvaughn#616) until a safer fix can be found.

* 🎉 New Masonry component optimized for Pinterest-style layouts. Chec…

…k out the docs (https://github.com/bvaughn/react-virtualized/blob/master/docs/Masonry.md) and demo page (https://bvaughn.github.io/react-virtualized/#/components/Masonry) to learn more. (bvaughn#618)

* 🎉 MultiGrid supports scrollLeft and scrollTop props for controlled scrolling. (@julianwong94 - bvaughn#624)
* 🎉 New direction parameter passed to overscanIndicesGetter with values "horizontal" or "vertical". (@offsky - bvaughn#629)
* ✨ Replaced inline require statement with header import in Grid for better integration with the Rollup module bundler. (@odogono - bvaughn#617)
* 🐛 Improved guard for edge-case scrolling issue with rubberband scrolling in iOS. (@dtoddtarsi - bvaughn#616)
* ✨ Replaced getBoundingClientRect() with slightly faster offsetWidth and offsetHeight inside of AutoSizer.
* ✨ AutoSizer no longer re-renders nor calls onResize callback unless width and/or height have changed (depending on which properties are being watched).